A gas turbine engine typically includes a nacelle that forms an opening to allow a determined stream of air to enter into the engine itself. The turbojet comprises a fan, adapted for providing initial compression of the air entering the engine, and one or more sections compressing the air allowed into the engine (generally a low-pressure section and a high-pressure section). The air thus compressed is allowed into the combustion chamber and mixed with fuel before being burned therein. The hot combustion gases arising from this combustion are then relaxed in different turbine stages (generally a low-pressure section and a high-pressure section).
Certain pieces of the engines comprise a protective surface coating in order to protect them from the environment. Typically, pieces made of composite material, for example comprising a fiber reinforcement densified by a polymer matrix, are usually covered on their surface with a protective coating in order to meet the requirements for resistance to the engine environment. Such composite material pieces can have complex geometry and can in particular comprise static vanes (guide vanes of the fan), movable vanes (fan vanes), or else casings, which complicates the application of their coating.
Currently methods for applying surface coatings to these different pieces are hard to reproduce. Specifically, these methods usually consist in gluing a protective film, for example a vulcanized polyurethane film, onto the surface to be protected. However, the thickness of the film and the glue is very hard to control, particularly by reason of the complicated geometry of the pieces, so that the dimensions of the final piece can vary greatly from one piece to the next. Moreover, their surface must be prepared beforehand for gluing the film by abrasion, specifically because of the material forming these pieces, which has a tendency to locally degrade the piece, to reduce the reproducibility of the method even further, and to increase the cost and duration of the method.
The choice of glue to be used is moreover made difficult insofar as the glue must observe two sometimes contradictory conditions. A first condition is that the glue must be able to be employed at a lower temperature in order not to damage the piece, and have an overall use temperature of less than a hundred degrees to avoid the matrix, generally made of polymer, degrading in the heat. A second condition is that the glue must have the highest properties possible, i.e. a degree of cross-linking approaching 100% in order to exhibit adequate mechanical properties of adhesion. It is therefore necessary to find a compromise between the preservation of the piece (lowest possible use temperature) and the properties of the glue (high temperature) to obtain optimal performance for the final piece, which in practice turns out to be difficult.
Finally, these known methods have the drawback of being polluting and requiring many expensive and bulky tools in order to observe environmental regulations concerning the protection of the operator, the limitation of volatile substances in the atmosphere etc.
It has also been proposed to apply the coating onto the piece by spraying material in the form of a paint. However, this method also requires the surface of the piece to be protected to be prepared beforehand (abrasion, reduction of surface defects by application of products intended to block the surface pores etc.), then a pre-layer to be applied in order to improve the adhesion of the paint onto the piece surface. However, each of these steps requires the employment of adapted spray guns. Moreover, the drying time of the various treatments must be observed and the piece surface must be sanded between each application. Finally, the method must be performed in controlled conditions, in order to control the temperature, hygrometry, and the level of volatiles in the atmosphere as well as the pollution risks.
The document U.S. Pat. No. 5,057,257, meanwhile, proposes a tool in accordance with the introduction of Claim 1. However, this tool does not make it possible to apply a protective coating to a surface of a piece that is easily reproducible.